Many apparatuses and methods have been advanced for the measurement of color vision in human subjects. Color lanterns, color threads, pseudo-isochromatic color charts and anomaloscopes.
Whereas the prior art apparatuses and methods deal with all general aspects of the problem, none offer a unique, simple, effective and portable laboratory-grade apparatus and method for routine use in a clinical setting.
As noted above, the testing of human color sense is important for diagnosis, and in particular, the testing of the color-differentiating capability of humans in the red-green range. The tests of the human color sense are today carried out mostly by pigment samples (for example, so called pseudo-isochromatic tables), with transparent color filter glasses (color test plate) or by mixing and comparing spectral lights with the anomaloscope according to Nagel. The anomaloscope of Nagel determines the capability of seeing colors in relationship to the seeing of red-green. The determination is made by comparing a binary mixture of a red and a green spectral light with a monochromatic yellow. From the mixture ratio and the adjusted luminous density of the comparison yellow, it is possible to recognize the color emmetropia of the person being tested with respect to seeing red-green. The anomaloscope according to Nagel has a mechanically very expensive construction. It also has already been suggested to use luminescence diodes for color tests, whereby two diodes of the same color are used, the brightnesses of which are modulated. From Offenlegungsschrift No. 32 09 455 it is furthermore known to use two luminescence diodes for a device of the quantitative testing of the color sense and its disorders, whereby one luminescence diode emits a yellow light and the second luminescence diode is a so called two-color luminescence diode, which emits both a red and also a green light. By mixing the red and the green, substantially monochromatic, light sources it is possible to simulate the color frequencies in the red-green range. In the practical design of such a device, the two luminous diodes are arranged relatively close to one another, such that the person being tested must judge these two luminous diodes with respect to their color characteristic and brightness. Experience has shown that the measured values obtained with such a device cannot be compared with the standardized values which are fixed in the norm.
The basic purpose of the invention is to provide a hand-held anomaloscope of the abovementioned type such that the same permits a standard testing corresponding with the anomaloscope of Nagel. In comparison to the known anomaloscope, the novel design is substantially simpler and thus less expensive to manufacture and offers the possibility of providing the person being tested a neutralizing white stimulus field between the individual measurements as suggested in U.S. Pat. No. 4,798,458.